Reduced-size vehicles such as ATVs and UVs are becoming increasingly popular in North America and the world. Historically, ATVs can trace their origins to motorcycles. The ATV began as a motorcycle with two rear wheels, called an All-Terrain Cycle (ATC) and then, due to safety considerations, evolved to include a second front wheel so as to become the conventional four-wheeled ATV. As ATVs have further evolved over the past twenty years, many other aspects of the vehicles have also been improved. Many of the improvements have concerned the driving performance of the ATVs (both in terms of operation of the vehicles in a straight line and over rough terrain). For example, ATVs have become equipped with larger and more powerful engines, sophisticated automatic transmissions, and advanced differential technology. The suspension systems, likewise, have matured from rigid mounted wheels and tires to long-travel, fully independent suspension systems.
Conventional reduced-size vehicles offered by a variety of manufacturers share a number of features in common with one another. Because reduced-size vehicles (and particularly ATVs) originated as offshoots of motorcycle technology, such vehicles in particular share certain features that are similar to those of motorcycles. In particular, a conventional ATV typically employs an internal structural frame formed by a group of struts, tubes, castings, and/or stampings (and/or other elements) that extend substantially parallel to one another from near the front of the vehicle to near the rear of the vehicle, generally in close proximity to a central longitudinal axis of the vehicle. The arrangement of struts is such that the overall frame would conform to (e.g., would fit within) the physical confines of motorcycles having long, narrow bodies, even though reduced-size vehicles such as ATVs and UVs typically have bodies that are substantially wider than those of motorcycles. Although through the years there has been a focus on reducing the cost of the frame, there have been few major innovations in frame design beyond the standard motorcycle design. The frame is seen as the structure that carries the critical vehicle systems but delivers little if any additional value to the end user.
In addition to having motorcycle-type frames, conventional reduced-size vehicles also have other features that reflect their evolution from motorcycles, for example, in terms of their cooling systems and exhaust systems. With respect to their cooling systems, conventional reduced-size vehicles typically employ engine cooling systems in which air flow moves horizontally along the vehicles as the vehicles move forward. More specifically, such engine cooling systems (which can include, for example, radiators or heat exchangers), are typically positioned within front or rear sections of the vehicles relative to the mid-sections of the vehicles in which operators are seated during operation. When placed in the front section of a vehicle, as is more commonly the case, cooling air enters at the very front end of the vehicle and typically is then exhausted into the mid-section/operator space. When placed generally in the rear section behind the mid-section, as is less commonly the case, cooling air enters from the mid-section/operator space and then passes out the vehicle's rear end.
As for the exhaust systems of reduced-size vehicles, the traditional motorcycle-based design and packaging of an ATV exhaust system places the muffler (which is generally round and cylindrical) at the rear of the vehicle, typically in a generally horizontal manner, with the outlet near or at the rear of the vehicle, facing aft or downward. Certain factors influence the exact positioning of the exhaust system configuration and muffler. First, the exhaust system should be configured to function within the confined area that an ATV allows after placement of the engine, cooling system, transmission, drivetrain, intake system, and other critical systems. Second, because ATVs are often operated in water, it is desirable to locate the outlet of the muffler as high as possible so as to minimize water intrusion. Third, the muffler should have sufficient volume to allow for adequate performance while maintaining satisfactory sound dampening qualities. Fourth, the exhaust outlet should be positioned so that the exhaust air is not discharged directly onto a person who is working in close proximity to the vehicle. Lastly, the exhaust system should be as small as possible, so as to minimize radiated heat, and should be heat-shielded and placed sufficiently far away from any operator (e.g., laced under a rear fender).
As reduced-size vehicles have grown in their size, power and capabilities, it has been recognized that the vehicles are suitable for performing a variety of chores and tasks for which ordinary cars, trucks, and tractors are not well suited. To facilitate the performing of these functions by reduced-size vehicles, it has further become desirable to create dedicated carrying/storage features on the reduced-size vehicles. Yet, because the primary consideration in designing reduced-size vehicles traditionally has been to enhance the vehicles' driving performance, the interiors of reduced-size vehicles (e.g., the volumes defined by the outer perimeters of the vehicles) have been completely or nearly completely filled with the various engine, powertrain, suspension, cooling and other system components allowing for optimal performance of the vehicles. To the extent that certain spaces within the vehicle interiors have been reserved for storage purposes, such spaces have typically been very small, e.g., with a volume of only about 3 gallons or less. As a result, such spaces typically are sufficient only for transporting small items such as a pair of gloves, a tow strap, or an emergency tool kit. Further, these spaces often are inconvenient to use, for example, because the ports/doors are located at low or otherwise difficult-to-access locations (e.g., under the seat), or because the doors are at low levels and lack seals to prevent the entry of water into the spaces.
Although at least one manufacturer, Bombardier, has integrated a somewhat larger, 8 gallon storage compartment into the front end of at least one of its ATV models (e.g., the 1999 Traxter ATV), this storage compartment is still limited in size due to the frame of the ATV and due to the positioning of the front shock absorbers of the vehicle, and there is no comparable storage compartment in the rear of the ATV due to the movement of certain components from the front end of the vehicle to the rear end of the vehicle to provide sufficient space for the front storage compartment. Also, although at least one other manufacturer, Arctic Cat, has integrated a somewhat larger, 8-10 gallon storage compartment into the rear end of at least one of its ATV models, this storage compartment is still limited in size due to the configuration of the vehicle frame and the positioning of the rear shock absorbers, as well as difficult to access insofar as it only occupies a region that is below the cargo rack accessible from behind the vehicle. Further, the storage compartment is located substantially above the locations at which the shock absorbers are coupled to the frame of the vehicle, and loading of that compartment with items/materials can raise the vehicle's center of gravity.
Given the lack of large internal carrying/storage spaces within conventional ATVs, ATV manufacturers have developed alternative features to enhance the ability of ATVs to carry and move items and material. In particular, ATV manufacturers have added cargo racks to the tops of the fenders, first at the rear sections of the vehicles and subsequently at the front sections of the vehicles. Depending upon the embodiment, a rack can be located on top of the bodywork of a vehicle, or in the case of a carrying bed, on top of the rear tires of a vehicle. The inclusion of such cargo racks on ATVs is now the industry standard. Additionally, although items can be strapped/tied directly to such cargo racks, to further enhance the cargo capacity of ATVs, it also has become common to purchase aftermarket storage containers that fasten to the tops of the cargo racks. Also, various enhancements have been developed for facilitating the coupling of items to cargo racks, for example, Artic Cat's “Speed Rack” and Polaris' “Speed Lock.” The use of such containers in combination with the cargo racks makes it possible to carry items/materials within enclosed compartments such that those items/materials are not exposed directly to the outside environment.
Although reduced-size vehicles with the above-described cargo rack and supplemental container features continue to increase in popularity, such conventional vehicles nevertheless have several limitations. First, the attachment of items/materials to the cargo racks is often challenging due to the need for additional ropes or cords or special clips to fasten the items. Second, in circumstances where containers are used, or otherwise large items are attached to the cargo racks, visibility can be reduced for the operators of the vehicles. Third, cargo carried on top of the racks can overload the vehicles and/or negatively impact the vehicles' centers of gravity, which in turn can impact the performance and safety of the vehicles. Indeed, this aspect is of particular significance to reduced-size vehicles in comparison with many other larger vehicles, both because reduced-size vehicles tend to be relatively light in terms of their weight, and also because reduced-size vehicles naturally tend to have a high center of gravity for other reasons—for example, because the vehicles typically are designed to have large amounts of ground clearance to clear obstacles while operating off-road, and because in such vehicles (particularly ATVs) the operator is seated upon the vehicle rather than within the vehicle. Consequently, the cargo racks/containers on reduced-size vehicles should be carefully loaded so as not to exceed the weight ratings of the vehicles.
Another limitation of conventional reduced-size vehicles is that the vehicles have little or no provision for floatation. ATVs in particular are frequently operated under conditions in which the vehicles need to ford bodies of water. During fording maneuvers, the depth of the water is not always known (e.g., if operating in an unfamiliar area). Consequently, it is not uncommon for an ATV to become submersed completely and ingest water into its engine and cease running, which is a significant inconvenience for the operator and can cause extensive damage to the engine. To prevent the above-described scenario, an ATV desirably would include sufficient displacement integrated into the vehicle to allow for vehicle floatation. Yet integrating sufficient displacement into an ATV for this purpose is difficult given the significant amount of displacement that is required. For example, typical ATVs weigh approximately 600 to 750 lbs without a rider, unladen. When a rider is positioned onto such an ATV, the ATV can approach as much as 950 lbs (e.g., supposing a 200 lb operator). Noting that the density of water is 8.34 lb/gal, an ATV needs to displace at least about 72 to 90 gallons of water to achieve buoyancy for the vehicle alone and potentially as much as about 114 gallons to obtain neutral buoyancy when laden with an operator (again supposing a 200 lb operator).
Conventional ATVs do include certain components that provide some buoyancy for the vehicles. Not only does the fuel tank in an ATV provide some buoyancy, but also virtually all ATVs employ the use of “high floatation oversize balloon tires” to provide buoyancy and, in some cases, pontoons or inflatable inner tubes can also be attached to the vehicles to provide additional buoyancy. None of these satisfactorily solves the buoyancy problem, however. The fuel tank only provides a limited amount of buoyancy, and the buoyancy that it provides varies depending upon how much it is filled with fuel. With respect to attaching pontoons/inner tubes to the ATVs, the use of such devices is undesirable for a variety of reasons including complications arising from the mounting/installation of those devices, negative effects on vehicle maneuverability when such devices are installed, and storage of the devices when not being used. As for the use of balloon tires, such tires on average only displace about 12 gallons of water each. Further, as the performance of ATVs is improved, there will continue to be an increased need for braking area, which will tend to drive up wheel size and reduce the available volume for the tires, which in turn will decrease the tires' overall contribution to buoyancy.
Even if one assumes that a typical ATV has four balloon tires, each displacing 12 gallons, and a typical fuel tank of 4 gallons (and no pontoons/inner tubes), and additionally that the remaining componentry/structure of a conventional ATV displaces an additional 20 gallons, such ATV will displace by way of these components only about 72 gallons of water or 600 pounds. Thus, noting the difference between the displaced weight of water and the typical weight of a conventional ATV, and given the density of water, a conventional ATV unladen (e.g., without any operator/passenger or additional carried weight) at best is barely buoyant and potentially falls short of neutral buoyancy by nearly 20 gallons. Further, with an operator on board, much less any additional weight, conventional ATVs will sink.
In addition to the aforementioned limitations relating to storage capacity and buoyancy, conventional reduced-size vehicles also are inadequate in terms of the manner in which the vehicles respond to accidents/impacts. More particularly, while the frames of conventional reduced-size vehicles are satisfactorily designed for the purpose of carrying the operator and the various internal vehicle systems, such conventional frames have not been designed with the aim of effectively dissipating energy if the vehicles hit immovable objects such as trees, or with the aim of reducing the effects of side impacts upon the vehicles. Further, because the struts/tubes, castings and stampings forming the frames of conventional reduced-size vehicles extend from the front ends to the rear ends of the vehicles in proximity to the central longitudinal axes of the vehicles, the frames are exposed to, and not particularly well-suited to resisting, extreme forces and torques that can be applied to the vehicles in certain accidents where the front ends of the vehicles tend to be twisted in directions contrary to those of the rear ends of the vehicles. In general, conventional frames have not been designed in a manner intended to enhance the crashworthiness of the reduced-size vehicles.
Further, the cooling systems of conventional reduced-size vehicles also have a number of drawbacks. With respect to conventional front-mounted cooling systems, for example, such systems are typically vulnerable to clogging in the off-road environment due to contact with mud, leaves, grass, snow, seeds, etc., and to the possibility of puncture from rocks & sticks. To the extent that extra guards are utilized to prevent puncture, these can exacerbate clogging events. Further, in such systems, the radiators exhaust heat into the mid-sections of the vehicles, which can undesirably heat up the seats and the surrounding bodywork and in some circumstances expose the vehicle operators (particularly the operators' legs) to undesirable heat. Additionally, when one such vehicle closely follows behind another such vehicle, the following vehicle can undesirably ingest dirty air expelled by the leading vehicle. As for conventional rear-mounted cooling systems, such systems are typically vulnerable to puncture and physical harm when the vehicles are driven in reverse. Such systems also can constrain suspension design and decrease vehicle system flexibility. To guarantee sufficient air flow, such systems often require large amounts of space within the vehicles to be dedicated to the communication of air for cooling and long coolant lines from the engine to the heat exchanger. Further, in contrast to the conventional front-mounted cooling systems, the rear-mounted cooling systems require fans to force air into the radiator, and hot air can “chimney” back to the operator if the cooling fan is not running
The exhaust systems of conventional reduced-size vehicles also have several drawbacks. First, the horizontal placement of a muffler in such a vehicle, in conjunction with the positioning of the muffler above the power cylinder(s) of the engine of the vehicle, allows water that has entered the muffler to drain directly into the engine (a condition that can regularly occur when operating the ATV in deep water and mud). Second, the horizontal placement of the muffler maximizes the surface area by which heat is convectively transferred away from the muffler and onto the plastic fender that is commonly located above it, which can result in significant and possibly undesirable heating of the fender. Although some reduced-size vehicles include heat shields above their mufflers and/or highly reflective foil insulators on the bottom sides of the plastic fenders, the fenders and surrounding body work of such vehicles often still can become undesirably hot. Further, even to the extent that the heating of the fenders and bodywork of such vehicles is reduced, the header pipes connecting the engines of the vehicles to their mufflers typically are run high in the vehicles, just below the edges of the operator seats and horizontally along the vehicles, e.g., proximate where operators' legs are situated during vehicle operation.
In view of the above discussion, it therefore would be advantageous if new reduced-size vehicles could be designed that overcame one or more of the aforementioned limitations. In particular, it would be advantageous if a new reduced-size vehicle was developed that could have one or more large interior storage compartment(s) for carrying items/material, where those interior storage compartment(s) were easy to use and/or were positioned substantially below the top of the vehicle such that items/material contained within those compartments did not overly raise the center of gravity of the vehicle or reduce operator visibility. Further, it would be advantageous if such a new reduced-size vehicle included features that improved the buoyancy of the vehicle. Additionally, it would be advantageous if such a new reduced size vehicle included an improved frame design to improve the vehicle's behavior under at least some accident conditions. Further, it would be advantageous if such a new reduced-size vehicle included an improved cooling system arrangement and/or improved exhaust system arrangement to alleviate one or more of the above-discussed problems associated with conventional reduced-size vehicles.